Comparison Of Thermal Performance Research Articles

Thermal performance appraisal of hybrid and nanofluid flow between a cone and a disk with variable thermal conductivity, viscous dissipation, and Joule heating

In many engineering systems, hybrid and nanofluids are influenced by their respective thermophysical characteristics. Lately, several models have been envisaged to foresee the hybrid and nanofluid attributes. The properties of hybrid nanofluids (HNFs) as potential heat transfer fluids are controlled by numerous aspects such as solid part size, volume fraction, and temperature. Considering the interesting facts of the hybrid and nanofluid flows, we in this exploration examined the thermal performance comparison of both types of fluid flows. The nanofluid and HNF are composed of molybdenum disulfide (MoS[Formula: see text]/kerosene oil and silicon dioxide–molybdenum disulfide (SiO2–MoS[Formula: see text]/kerosene oil, respectively. The flows are taken in a canonical gap between the cone and the disk. Both the cone and the disk may be rotating or stationary. The novelty of the computational model is enhanced by discussing the effects of viscous dissipation, Joule heating, and the variable thermal conductivity with convective condition. The Tawari and Das model is designed to analyze the heat transfer performance of the assumed fluid flows. The assumed fluid model is transmuted into the set of differential equations that are dealt numerically with the bvp4c MATLAB approach. The results are displayed in tables and graphical forms. For elevating estimations of the Eckert number, the heat transmission rate is found to be more significant in the disk than cone. It is also learned that hybrid nanoliquid heat transfer performance outperforms nanoliquid. The fluid velocity increases by raising the nanoparticle volume fraction [Formula: see text], and is decreasing for a higher magnetic field parameter. With the elevating estimates of thermal conductivity, it is shown that the cone transmits heat more quickly whereas the disc transmits heat more slowly. The thermal conductivity parameter increases the probability of collision of the liquid particles, that ultimately upsurges fluid heat transmission rate.

Enabling cross-morphological performance comparison: A case study in heat management design

Cross-morphological performance comparisons in mechanical engineering design may well resemble comparisons of apples and oranges. They are meaningful only if pertinent properties shared across compared morphologies (so-calledtertia comparationis) are identified, and equity with regard to these properties is established. This article demonstrates such an approach with the use of parametric geometry modeling, optimization, and additive manufacturing, enabling a thermal performance comparison of different heat sink morphologies, using both steady-state numerical simulation and experimental evaluation, by establishing equity across the compared heat sinks in terms of (thermal) mass. Limitations in additive manufacturing precision, as well as inconsistencies between numerical simulation and experimental evaluation results, were encountered in this case study. Likely resulting from the heat sinks’ thermal properties on the additive manufacturing process and the simulation environment’s disproportionate reliance on convection surface area, these limitations and inconsistencies will likely diminish as additive manufacturing and numerical simulation technologies improve. The cross-morphological comparison approach presented here is shown to be viable in principle and may inform decision-making in applied mechanical engineering design research and practice.

Comparison of thermal hydraulic performance between horizontal and vertical steam generators in nuclear power plants

Abstract Steam generators (SG) for Nuclear Power Plants (NPPs) are important large-sized metal consuming equipment of nuclear power installations. Efficiency of steam generator operation determines the overall service life of the whole nuclear facility. Vertical steam generators are used normally in North America, Europe and South East Asia, but horizontal steam generators are currently of great importance to reduce building heights and construction costs that govern the overall cost of new nuclear power plants. The objective of the current study is to measure the performance of nuclear steam generators in NPPs through comparative assessments of vertical and horizontal configurations. For this purpose, the vertical U-tube steam generators of a typical 4-loop Pressurized Water Reactor (PWR) was replaced by a VVER-1000 horizontal steam generators to evaluate the horizontal SG performance, at the same plant conditions and characteristics, in comparison with the vertical SG. The thermal hydraulic system code RELAP5 was used in the current work to perform the required analysis, during steady and transient scenarios.

Use of “Glass Curtain” Systems to Improve the Energy Efficiency and Thermal Comfort of Dwellings in a Warm Semi-Arid Mediterranean Climate

The dry Mediterranean climate (BShs) within a warm semi-arid climate (BSh) is the zone in Europe with the most annual hours of sunlight, and it has a smaller annual temperature variation than most climates. This allows the greenhouse effect caused by windows to be used to heat dwellings in winter. Balcony frameless retractable glazing systems known as “glass curtain” systems offer the highest proportion of glass and maximum openness in the façade, allowing for maximum sunlight and ventilation. This work studies a glazed terrace with a “glass curtain” in a dwelling on the Spanish Mediterranean coastline. The objective is to quantitatively determine the enhancement of the thermal comfort and energy efficiency of a dwelling using “glass curtain” systems. The modification of several design parameters of the glazed terrace is also analysed. The novelty of this study lies in demonstrating that the use and optimised design of “glass curtain” systems allows us to obtain nearly zero-energy buildings (nZEBs) and thermally comfortable dwellings all year round. The research methods include a comparison of the current thermal performance of the dwelling with and without a “glass curtain” system via on-site measurements. The study also evaluates the influence of modifying design parameters using computer simulations. The results show that “glass curtain” systems increase the indoor temperatures inside the dwelling by about 4 °C in winter and reduce the annual indoor thermal oscillation from more than 16 °C to only 10 °C. Consequently, such systems reduce heating energy needs by almost 60%. Glazed terraces using the proposed design parameters show further improvement regarding thermal comfort and practically eliminate heating and cooling needs.

Thermal performance comparison and new layout scheme study of high geothermal tunnel insulation layer

In order to solve the problem of designing the thermal insulation layer for high geothermal tunnels, this paper studies the nature of thermal insulation materials and the structure of the thermal insulation layer. Based on the mechanisms of heat transfer from the cylinder wall and the flat plate, combined with the physical and thermophysical properties of the materials tested, the selection of thermal insulating materials for high geothermal tunnels as well as the layout were analyzed. The results of the study showed that polyurethane materials proved to be a better overall insulation material, with better water resistance and lower thermal conductivity, as well as better compressive strength. The flat plate heat transfer model can be used to predict the temperature distribution of the lining structure, which simplifies heat transfer calculations and analysis. This paper proposed a new insulation design solution using polyurethane-corrugated steel insulation lining with a double layer deployment. Numerical simulation results show that the thermal insulation design scheme can effectively reduce the temperature of the lining structure, which is beneficial to improve the thermal performance of the lining structure. The results of the study may provide new ideas for the design of heat-insulating structures for high geothermal tunnels.

Energy and enviro-economic analysis of a solar air heater with wedge turbulators.

Solar air heaters (SAH) convert solar energy to thermal energy for food processing industries and commercial space heating applications, as solar energy is cost-free. In this experimental study, the thermal performance of the solar air heater has been successively improved using different roughness elements over the absorber. The triangle-shaped wedges in three structures (inline, serpentine, and clustered structure) are investigated in this work. Thermal performance comparison is made with a SAH with a plain absorber. A maximum air temperature rise of 19°C is observed for the SAH with wedges in a clustered structure. The absorber surface temperature for clustered structured roughness elements is 76.8°C with an average heat loss coefficient of 4.43 W/m2·K. The useful heat absorption using clustered structure wedges is 33%, 17.9%, and 6.6% higher than the SAH with plain, inline, and serpentine structured wedges. SAH's maximum thermal and exergy efficiency with clustered structured elements is 70.4% and 1.64%. The average thermal efficiency of inline, serpentine, and clustered arrangement is 13.3%, 25.3%, and 35.6% higher than the SAH with a plain absorber. The proposed SAH design shows a sustainability index 1.01, and lower payback periods show economic and environmental viability.

Comparison of thermal performance in solution heat exchangers with different chevron angles in absorption system

In this study, a solution heat exchanger (SHEX), one of the components of LiBr–H2O absorption refrigeration, is selected as a 60° and 30° chevron angle brazing-type plate heat exchanger, and its performance is experimentally investigated. The result shows that as the mass flow rate of the strong solution side increased, the heat transfer rate increased significantly. When the chevron angle is 60° in the SHEX, the overall heat transfer coefficient, j-factor, differential pressure, f-factor, and JF-factor of the solution heat exchanger increased by 86%–149 %, 72%–180 %, 221%–376 %, 220%–378 %, and 16.6%–66.2 %, respectively, compared with the SHEX with a 30°-chevron angle. The SHEX with a 30°-chevron angle shows a 138%–221 % higher performance index than that with a 60°-chevron angle. In addition, the Nusselt number prediction correlation of the SHEX, including various chevron angles and Reynolds numbers, was proposed, which can provide essential information for designing SHEXs in actual absorption systems.

Thermal Performance Evaluation of Trapezium Solar Cooker with Hexagonal Solar Cooker

Abstract: Energy has become the utmost necessity of our life. It is required from dawn to dusk to fuel the world. Energy is scattered everywhere around the Earth. Energy has always been an inextricable part of human life. The existence of living organisms on the earth is possible due to the solar radiations reaching the earth and the ozone layer that makes the most favorable temperature required for the functioning of enzymes and led to the existence of life and other sources required for supporting the survival of life. The present work aim on fabrication of trapezium and hexagonal cooker and their thermal performance comparison to evaluate based on their temperature values using K type thermocouples.

The thermal and energy performance comparison of extruded polystyrene foam insulation for an apartment building in different climate zones,Egypt

The thermal and energy performance comparison of extruded polystyrene foam insulation for an apartment building in different climate zones,Egypt

Evaluating the sustainable features of vernacular architecture in hot-arid regions: field surveys and analysis in two vernacular houses in Al Batinah region (Oman)

ABSTRACT The necessity to derive sustainable building solutions from the local vernacular architecture is being increasingly asserted in the global debate about the immense energy consumption, natural resources depletion, and high levels of Green House Emissions (GHG). Paradoxically, a limited number of research has addressed this issue in the arid hot regions and much less in the Arabian Peninsula. As a contribution to this debate, the present paper evaluates the sustainable features present in the Omani vernacular houses and their efficacy in terms of thermal comfort and energy performance. A Methodology that combines on-site measurements with modelling simulations, using DesignBuilder software, was applied to achieve the three objectives assigned to this study: (a) Characterization of Vernacular Architecture in Oman and its bioclimatic features, (b) Evaluation of the thermal and energy performance of a selected vernacular house. (c) A comparison of thermal and energy performance between a vernacular dwelling and a contemporary Omani house. The numerical simulation confirmed that the vernacular construction system provides enhanced thermal performance when compared to its modern counterpart. It has also been showed that the house with a vernacular construction system requires twice less cooling energy than its modern counterpart.

Experimental thermal performance comparison of the same ORC system operated in Harbin and Taipei

Experimental thermal performance comparison of the same ORC system operated in Harbin and Taipei

Comparison of thermal and electrical performance in a HCPV system based on spray cooling

As a renewable energy, solar energy can effectively solve the energy crisis. Improving the efficiency of thermal and electrical conversion is of significance to high concentration photovoltaic/thermal (HCPV/T) systems. For further reducing the contact thermal resistance in the HCPV/T systems, this paper presents an integrated system of HCPV system and spray cooling (SC-HCPV). A comprehensive heat transfer model was established to study the influence of heat on solar cells by combining solar cells with spray cooling (SC). The temperature uniformity, thermal and electrical performance at high concentrations is studied through experiments and simulations. The influences of nozzle settings, concentration ratio (CR) and inlet temperature are evaluated to get suitable system operating parameters. Compared with the partial jet, the EEF under SC is 2.1% higher than that under the partial jet, and the solar cell power generation per unit area can gain 7.5%. For another aspect, the EEF of the system can still maintain above 30% under the high CR of 1000, and high-temperature hot water above 60 °C can be obtained, which has superior potential applications in printing and dyeing, domestic water with high temperature, seawater desalination, disinfection water and so on.

Comparison of Thermal Performance between Annular Fins and Longitudinal Fins in Latent Heat Storage Unit

Comparison of Thermal Performance between Annular Fins and Longitudinal Fins in Latent Heat Storage Unit

Prefabricated thermally-activated fiber-polymer composite building slab P-TACS: Toward the multifunctional and pre-fabricated structural elements in buildings

The traditional sequential design of building elements, where every element performs only one dedicated function, carries significant embodied energy. Thus, modular pre-fabricated load-bearing elements could overcome the disadvantages of the current carbon-intensive construction practice and go beyond; as such, lightweight glass fiber-polymer composite profiles could be more advantageous in performance. Cellular structures of such profiles can be advantageous for adding water channels for active heating and cooling indoors and for fire protection. Therefore, the development of such a modular active building slab referred to as P-TACS (Prefabricated Thermally-Activated Fiber-Polymer Composite Slab) is explored in this work. The structural performance of a proposed P-TACS design is verified in terms of serviceability and ultimate limit states. The addition of local carbon fiber inclusions allows for an increase in the span of the slab to 10 m and a more uniform surface temperature. Thermal performance of the structurally optimized geometrical configuration is analyzed by, first of all, determining water parameters based on the 1D approach partially adopted from the standard radiant systems analysis and, secondly, by a detailed 2D thermal analysis using ANSYS Fluent numerical simulations. The hydraulic and thermal performance comparison of the novel P-TACS design with two standard radiant systems (ESS Type A and RCP) reveals that the P-TACS design outperforms the standard embedded surface system ESS Type A, both for floor heating and cooling case. In addition, the response time of P-TACS is three times faster compared to the ESS response time. The main advantage of the P-TACS is in lower mean water temperature, compared to traditional embedded radiant systems (e.g., EES type), required for conditioning the space, potentially resulting in lower operational energy use. The fire outbreak scenario is considered to complete the analysis, and the measures to switch water flow from nominal to fire scenario are proposed.

Evaluation and comparison of thermal performance of latent heat storage units with shell-and-tube, rectangular, and cylindrical configurations

• Criteria are proposed to evaluate heat transfer, flow resistance, and irreversibility. • Shell-and-tube LHSU has the shortest phase change time and highest heat transfer rate. • Shell-and-tube LSHU achieves the highest j / f factor and the best thermal performance. • Cylindrical LHSU achieves the highest melting exergy efficiency of 81.5% • Shell-and-tube LHSU has the highest exergy efficiency of thermal store-release cycle. Latent heat storage plays a significant role in tackling the mismatch between energy supply and demand. Evaluation and comparison of the thermal performance of different shaped latent heat storage units (LHSU) are essential in the optimal design of LHSU. This study developed the numerical model of heat transfer and flow in shell-and-tube, rectangular, and cylindrical LHSU with the same PCM mass and heat transfer area. Two kinds of criteria, namely the j / f factor considering both heat transfer and flow resistance and the exergy coefficient evaluating irreversibility, are proposed to assess the performance of LHSU comprehensively. It shows that natural convection intensity in cylindrical LHSU is the highest, while the shell-and-tube LHSU exhibits the lowest phase change time and the highest heat transfer rate. The average j / f factor of shell-and-tube LHSU is 21.4% larger than that of rectangular LHSU and is twice as much as that of cylindrical LHSU. Therefore, the shell-and-tube LSHU achieves the best overall thermal performance. Moreover, cylindrical LHSU achieves the highest melting exergy efficiency of 81.5%, while shell-and-tube LHSU has the highest solidification exergy efficiency of 62.8%. Regarding the thermal storage and release cycle, the exergy efficiencies of shell-and-tube, rectangular, and cylindrical LHSU are 50.1%, 49.2%, and 48.5%, respectively. Therefore, shell-and-tube is the optimal shape to achieve the largest exergy efficiency of the thermal storage-release cycle. This study deepens the understanding of the thermal behavior of PCM packed in different shaped containers, obtains the optimal geometric configuration, and gives guidance to the optimal design of geometric parameters of the LHSU.

Thermal performance of cross-laminated timber (CLT) and cross-laminated bamboo and timber (CLBT) panels

ABSTRACT Cross-laminated timber (CLT) is increasingly being utilized in Europe, North America and elsewhere due to its superior mechanical properties and environmental-friendly performance. Considering regions and countries, such as China, those are scarce in structural wood resource but rich in bamboo forest, an idea of introducing bamboo into CLT system has been proposed to form a novel composite material, named as cross-laminated bamboo and timber (CLBT). This paper focuses on the comparison of thermal insulation performance of CLBT and CLT panels. The thermal resistance and transmittance of CLT and CLBT wall specimens were measured by the Guarded Hot Box test. A calculation method provided by ISO standard and a finite element (FE) model were also used to evaluate the thermal resistance of CLT and CLBT panels. Based on the proposed FE model, some parametric analysis was performed through 11 CLBT panels with different compositions, including the layer number of glubam and timber, the thickness of extruded polystyrene and the use of gypsum board and screws. Moreover, the feasibilities of these CLBT panels were evaluated for the application in different climate regions of China and the United States in accordance with the corresponding Chinese and American building energy efficiency standards, respectively. It can be finally concluded that, the development and application of CLBT contributes to achieving the low carbon sustainable features of structures, which is due to the good carbon sequestration ability of its component materials (i.e., timber and bamboo) as well as the good insulation performance of CLBT panels.

Fluid flow and heat transfer in a rectangular ribbed channel with a hierarchical design for turbine blade internal cooling

• New design concept to develop high-performance internal cooling of turbine blades. • Greatly reduced pressure loss is achieved with negligible heat transfer reduction. • The underlying physics of pressure drop and heat transfer performance is clarified. • Various designs are examined to verify the feasibility of the new design concept. For internal cooling of a turbine blade, various advanced rib turbulators can markedly contribute to the heat transfer enhancement while suffering a great increase in pressure loss. In those designs, ribs with the same configuration are periodically and evenly mounted on the channel wall. In this context, this work proposes a hierarchical design concept to optimize the rib arrangement with the desired reduction in pressure loss. In terms of the rib height, this new design concept is implemented to construct three new rib configurations. Based on an established turbulence model, three-dimensional (3D) numerical simulations are entirely adopted to verify the feasibility of the new configuration in a wide Reynolds number range. The numerical results demonstrate that the optimal configuration with a linearly decreasing rib height can greatly reduce the pressure loss with a slight heat transfer deterioration. The negligible reduction in the heat transfer performance results from the enhanced fluid impingement on the reattachment region because of the lowering effect of the mainstream, although small ribs weaken the fluid impingement. The marked pressure drop reduction comes from the combination of the lowering effect and small ribs which constrains the separation vortex behind ribs. Furthermore, the comparison of the overall thermal performance is carried out considering a wide range of the Reynolds number, pitch ratios, and aspect ratios. The optimal configuration can greatly enhance the overall thermal performance up to 138.3% for the factor ( Nu / Nu 0 )/( f / f 0 ) and up to 32.5% for the factor ( Nu / Nu 0 )/( f / f 0 ) 1/3 . Eliminating the entrance effect of developing flow, the increment in the overall thermal performance is considerably reduced but still keeps at a high level. Finally, it is significantly highlighted that as a simple but effective improvement, the hierarchical design concept presents great potential in developing high-performance internal cooling of turbine blades.

Numerical comparison of thermal energy performance between spouted, fluidized and fixed beds using supercritical CO2 as fluidizing agent

The different thermal energy performance between spouted, fluidized, and fixed beds when using supercritical CO2 as a fluidizing agent was numerically investigated by employing a combined approach of Computational Fluid Dynamics (CFD) and Coarse-Grained Particle (CGP) methods. The model was first validated against experimental data available in the literature, confirming that the simulated particle velocity and temperature agreed well with the experimental measurements. The numerical results reveal that for the spouted bed, gas velocity, gas temperature, and convective heat transfer were higher in the spout region. Hence, most heat was transported directly from the inlet to the outlet of this system. For the fluidized bed, the particles near the gas inlet were quickly heated up at first, and a uniform temperature distribution was achieved in the whole bed during the later stages of the process. Concerning the fixed bed, its behavior is well-known with three temperature zones differentiated, which are a hot region, a cold zone, and the intermediate thermocline. Besides, numerical simulations allow further analysis in detail of the different heat transfer mechanisms in the configurations tested. Convection is the dominant mechanism in all cases. Conduction is noticeable in the fixed bed regime compared to the spouted or fluidized regimes, but even in this case, it is still an order of magnitude lower than the convection mechanism. Finally, thermal energy and exergy were also analyzed for the three beds.

Performance Investigation of Cylindrical Cavity Receiver Using Roughened Surfaces

Solar cavity receiver is an integral part of the solar parabolic dish collectors used for absorbing concentrated solar irradiation. The performance of the receivers can be enhanced utilizing different types of heat transfer fluids (HTF) and modified geometries. The thermal performance of a redesigned cavity receiver with solid semi-circular tube attached to its surface was investigated using CFD three-dimensional simulation. The influence of operating and geometric parameters (i.e., inlet mass flow rate and inlet temperature) were investigated. The results obtained shows that, redesigned solar cavity receiver has thermal efficiency of 8.49-10.27% higher than a normal cavity receiver with an inlet flow rate of 0.01-0.04 kg/s under the same environmental and operating conditions. The temperature of outlet of HTF increases with increases in inlet temperature for Therminol66 oil. The comparison of thermal performance using different HTF (i.e., Therminol66, Ethylene Glycol, Water) is also conducted and it is found that Therminol66 oil gives 9% and 17% higher outlet temperature than ethylene glycol and water respectively at intake flow rate of 0.02 kg/s.

Performance comparison appraisal of a fully wetted longitudinal fin of different profiles with variable thermal conductivities

The goal of this study is to examine the thermal performance and the flow of hybrid nanofluid over three types of longitudinal wetted fins encompassing thin tip fin, thick tip fin, and fin with a rectangular shape. It is pertinent to mention that both thin and thick tip fins are of exponential profile. The longitudinal fins are of variable thickness with stagnant, stretching, and shrinking cases in a fully wetted circumstance to study the heat augmentation of a conveyer belt. The previous studies considered constant temperature but, in this analysis, the variable type (temperature-dependent) i.e., exponential and linear forms of thermal conductivities are cogitated for all three cases. A comparison of thermal performance is also elaborated for variables thermal conductivities considering the above-cited three cases. The analysis would be more useful in the designing of fin structures that are helpful to enhance thermal efficiency. This is a pioneering study in this direction. The mathematical model is elucidated numerically. The impact of arising pertinent parameters is arbitrated. It is examined that inverted and rectangular fins possess more heat transfer rate in comparison to the tapered fin. Furthermore, the surface temperature of the stretching fin is higher than the shrinking fin.